This invention relates to an apparatus for identification of individuals by making use of a data base of their facial images that are inputted from a video camera and the like.
A typical apparatus, so far existent, for identifying an individual by means of reading his facial image is the one as carried ill the official gazette Japanese Patent Laid-Open No. 63-177273. The setup of the aforementioned apparatus is explained in the following:
FIG. 2 is a block diagram showing an example of the conventional apparatuses for identifying an individual by reading his facial image. Item 11 is a visual image input unit to input a facial image, item 12 is a characteristics extracting unit consisting of an A/D converter, a central processing device, a memory, etc., item 13 is a data base of individuals wherein characteristic points of each individual's face are stored and item 14 is an information processing unit wherein the differences obtained through comparing pieces of the information from the characteristics extraction unit 12 with the characteristic information from the data base of individuals 13 are detected and utilized for a correct recognition of a particular individual in question by checking the magnitude of the differences to determine whether it is exceeding a certain threshold value or not.
According to the conventional technology as described in the foregoing, recognition of an individual is carried out by detecting the differences between the characteristic points of a facial image inputted from the visual image input unit 11 and those of the facial images stored in the data base of individuals 13 through the information processing unit 14 and by making a judgment on the magnitude of the differences. However, when the facial expressions are different between the facial images stored in the data base of individuals 13 and the image inputted from the visual image unit 11 in the aforementioned case, the differences between the two kinds of characteristic points tend to become so large that the same single person is sometimes recognized as two separate individuals. In order to prevent this wrong recognition from taking place., it is necessary to select characteristic points that are not likely to be affected by changes in facial expressions. However, the characteristic points less affected by facial expressions are limited to a small number of places such as the both ends of an eye, the nose top, etc. As the number of characteristic points decreases, there exist more risks of identifying the same single person as two different individuals.
According to a prior art as described in U.S. Pat. No. 4,975,969, recognition of a correct person is carried out by the steps of first calculating the positions of respective centers of right and left irises, nose top, and center of mouth, and then making use of the distances between right iris and nose, left iris and nose, right iris and mouth, left iris and mouth, and nose and mouth respectively, all the distances being normalized by the distance between right and left irises. However, no information of expression muscles is utilized in this case, therefore resulting in a problem of deterioration in accuracy due to shifting of the center position of mouth or the like caused by changes in facial expressions.
This invention relates to a method of identifying an individual correctly by utilizing even a facial image of abundant expressions without resorting to a reduction of characteristic points in solving the above mentioned problem.